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    <title>Document</title>
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<body>
    <script>
        const obj = {
            b: 2
        }

        Object.defineProperties(obj, {
            a: {
                get() {
                    console.log("运行了属性a的get函数")
                    return obj._a
                },
                set(val) {
                    console.log("运行了属性a的set函数", val)
                    obj._a = val
                }
            }
        })

        // obj.a = 20 + 10; // set(20 + 10)
        // console.log(obj.a); // console.log(get())

        // obj.a = obj.a + 1; // set(obj.a + 1)   set(get() + 1)
        // console.log(obj.a);

        // console.log(obj.a)

        obj.a = 10;
        console.log(obj);
    </script>
</body>

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